As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
One or more cooling fans are typically employed within the electronic chassis enclosure of information handling system platforms, such as servers, to cool components operating within the information handling system chassis. Such cooling fans may be uncontrolled, i.e., running at full power whenever the information handling system is a powered on state. However, cooling fans consume power, create noise, and create airflow, each of which becomes of greater concern in a data center where a plurality of information handling system platforms may be operating, e.g., as servers. Cooling fans may also be controlled based on ambient temperature within an information handling system chassis enclosure.
As thermal control of electronic enclosures has evolved it has become common for discrete mapping of thermal sensors directly to a cooling fan zone defined within an enclosure. This allows for localized component cooling requirements to be directly coupled to discrete fan/s, minimizing system acoustic and fan power compared to having a single system fan zone. By mapping component cooling requirements to a fan zone instead of to all system fans, cooling fan power savings greater than 25% can be achieved. However, there are disadvantages associated with mapping a component to a single fan zone. For example, when a component is directly mapped to a single fan zone, thermal requirements for the component can only be affected by increasing cooling fan speeds for this single zone. This limits local airflow potential and can lead to higher fan power for component cooling.
It is known to employ a flexible weighted mapping of component cooling requirements to cooling fan zones, with weighted mapping of fan zones to each other. Fan mapping between fan zones can be a percentage, an offset, or a combination of the two. For example, a known equation for pulse width modulation (PWM) cooling fan mapping used in a thermal control algorithm is given below:Fan Zone Mapping: PWM_Config(PWM(zone))=a*PWM(zone)+c 
By applying weighted fan zone mapping, cooling can be optimized for power consumption as function of component thermal requirements by reducing maximum fan speeds. Since fan power is a cubic of fan speed, decreasing maximum fan speeds can reduce system fan power even if other adjacent fan speeds are increasing.
For modular information handling systems, each module may have a pre-defined set of fans in a given fan zone that are the primary assigned fans for the given module. Remaining (secondary) fans in the modular chassis can be controlled based on the speed of the fans in the given fan zone. In this regard, the secondary fans within a modular chassis enclosure may be set to a speed that is a fixed function of the current speed of the primary cooling fans of the given module fan zone. One such conventional fan mapping approach controls secondary fan speed using a hard-coded or static fixed percentage value that is taken from a thermal table and which is obtained by thermal characterization run mainly for worst-case system thermal configurations. Using this approach, the fan speed of the secondary fans are controlled to be a fixed percentage of the fan speed of the primary fans in the given module fan zone. For example, secondary fan speed may be controlled to always be a fixed percentage of the current fan speed of the primary cooling fans within the given module fan zone. In another conventional “all or nothing” approach, secondary fan speed may be switched back and forth between a fixed percentage of the current primary fan speed of the given module fan zone, and an independent fan speed that is not dependent or based on the current fan speed of the primary cooling fans within the given module fan zone.
Controlling secondary fan speed to be a static fixed percentage of the current speed of the primary cooling fans of a given module fan zone is a conventional “one size fits all” approach that does not account for component variation or for different steady state conditions. In this regard, the static percentage value may prove sub-optimal from a power savings perspective for configurations other than the ones tested during system development. In addition, it is difficult to tune the static percentage value during thermal development due to huge number of different configurations & factors. Further, there is a thermal risk of airflow recirculation if the static fixed percentage values are incorrectly chosen to be too low.
Another conventional methodology implemented in blade server enclosures begins by not controlling any secondary fan speed based on the current speed of a primary cooling fan. If the chassis management controller (CMC) of the blade server enclosure detects a blade fan speed request of 100% for longer than a set time period, it quickly ramps up secondary fans to 100% to provide additional airflow. This solution is prone to fan speed oscillation.